Look up Tacoma Narrows bridge. It's not the wind speed but a frequency
oscillation of the wind that might excite the natural frequency of the rig.
Neil Schiller
1970 Redwing 35, Hull #7
(C&C 35, Mark I)
"Corsair"
Retired Mechanical Engineer
On 7/31/2015 10:26 PM, Jim Watts via CnC-List wrote:
On our latest trip north, we anchored in Clam Bay and had a strange
problem. At a certain wind speed, the shrouds would start to hum,
sometimes making the boat shake with vibration. The major vibration
was felt in the small rod running to the underside of the upper
spreaders and in the mast and backstay. I backed each shroud one off
half a turn and it really didn't do much except make those shrouds
look loose to me, but I'm sure I can't tell the difference of 1/128th
of an inch. It eventually faded as the wind dropped.
For the next ten days, in all sorts of conditions, we didn't hear it,
but when we anchored in the same bay 10 days later, we got it again.
Any explanation except witchcraft?
Jim Watts
Paradigm Shift
C&C 35 Mk III
Victoria, BC
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